1. Field of the Invention
The present invention generally relates to methods, systems and software product used in the area of computer-aided engineering analysis, more particularly to numerically simulating inflation of an airbag configured with a plurality of connected flexible-boundary volumes (e.g., an airbag having more than one connected pouches for protecting occupants in an automobile during a car crash).
2. Description of the Related Art
Continuum mechanics has been used for simulating continuous matter such as solids and fluids (i.e., liquids and gases). Differential equations are employed in solving problems in continuum mechanics. Many numerical procedures have been used. One of the most popular methods is finite element analysis (FEA), which is a computerized method widely used in industry to model and solve engineering problems relating to complex systems such as three-dimensional non-linear structural design and analysis. FEA derives its name from the manner in which the geometry of the object under consideration is specified. With the advent of the modern digital computer, FEA has been implemented as FEA software. Basically, the FEA software is provided with a model of the geometric description and the associated material properties at each point within the model. In this model, the geometry of the system under analysis is represented by solids, shells and beams of various sizes, which are referred to as finite elements. The vertices of the finite elements are referred to as nodes. The model is comprised of a finite number of finite elements, which are assigned a material name to associate with material properties. The model thus represents the physical space occupied by the object under analysis along with its immediate surroundings. The FEA software then refers to a table in which the properties (e.g., stress-strain constitutive equation, Young's modulus, Poisson's ratio, thermo-conductivity) of each material type are tabulated. Additionally, the conditions at the boundary of the object (i.e., loadings, physical constraints, etc.) are specified. In this fashion a model of the object and its environment is created.
One of the most challenging FEA tasks is to simulate an impact event such as car crash. As the modern computer improves, engineers not only wish to simulate the vehicle behavior in a car crash, they also want to simulate the occupant safety device such as airbag deployment during a car crash.
Traditional airbag is generally configured with one large bag, which is inflated with an explosive blast when a sensor detects a sudden de-acceleration such as a car crash. In certain situations, the heat generated by an explosive blast could cause a burn of the occupant's body when contacted with a rapid developing airbag.
A number of new approaches have been developed to solve this problem. One of them is an airbag configured with more than one connected pouches. The airbag is configured such that a primary pouch acted as a master is initially inflated by the blast. Then the secondary pouch is inflated by the air flowed through the connected openings between the primary and secondary pouches. Additionally, the secondary pouch is configured with outside openings to allow ambient air to be drawn in during the deployment of the secondary pouch. Since the secondary pouch does not receive the heat of the blast directly, it is less likely to cause a burn of the occupant's body.
However, there is no computer or numerical simulation method today that can properly simulate the inflation of such airbag. It would therefore be desirable to have new improved method and system for simulating inflation of an airbag having more than one connected flexible-boundary volumes.